Partonic Contributions to the Proton Spin in Lattice QCD

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dc.contributor.advisorJi, Xiangdongen_US
dc.contributor.authorZhao, Yongen_US
dc.contributor.departmentPhysicsen_US
dc.contributor.publisherDigital Repository at the University of Marylanden_US
dc.contributor.publisherUniversity of Maryland (College Park, Md.)en_US
dc.date.accessioned2015-09-18T05:37:35Z
dc.date.available2015-09-18T05:37:35Z
dc.date.issued2015en_US
dc.description.abstractIn Feynman's parton picture, the proton spin can be understood as sum of the contributions from the spin and orbital angular momentum of the quark and gluon partons. However, in gauge theories, there is no local gauge-invariant notion of the spin or orbital angular momentum of the gauge particles. It is shown that in the infinite momentum frame of the proton, the gluons can be equivalent to free radiation, which is analogous to the Weizsaecker-Williams approximation in electrodynamics, and therefore one can talk about gluon helicity and longitudinal orbital angular momentum. We will justify the physical meaning of the Jaffe-Manohar sum rule for the longitudinal proton spin which uses the free-field expression of the QCD angular momentum operator in the light-cone gauge. Furthermore, it is discovered that each term in the Jaffe-Manohar sum rule can be related to the matrix element of a gauge-invariant, but frame-dependent operator through a factorization formula in large-momentum effective field theory. This provides a new approach for the nonperturbative calculation of the proton spin content in lattice QCD, and can be applied to the other parton observables as well. We present all the matching coefficients for the proton spin sum rule and non-singlet quark distributions at one-loop order in perturbation theory. These results will be useful for a first direct lattice calculation of the corresponding parton properties, especially the gluon helicity and parton orbital angular momentum.en_US
dc.identifierhttps://doi.org/10.13016/M2QH0B
dc.identifier.urihttp://hdl.handle.net/1903/16934
dc.language.isoenen_US
dc.subject.pqcontrolledNuclear physics and radiationen_US
dc.subject.pqcontrolledParticle physicsen_US
dc.subject.pqcontrolledTheoretical physicsen_US
dc.subject.pquncontrolledGluon polarizationen_US
dc.subject.pquncontrolledLarge-momentum effective theoryen_US
dc.subject.pquncontrolledLattice QCDen_US
dc.subject.pquncontrolledOrbital angular momentumen_US
dc.subject.pquncontrolledParton distributionen_US
dc.subject.pquncontrolledProton spinen_US
dc.titlePartonic Contributions to the Proton Spin in Lattice QCDen_US
dc.typeDissertationen_US

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